Lenovo ideapad 5 windows 11 update disable charging circuit?

[bogart219]

That's bad if the resistance measurement is correct


PQ6204 is the high side MOSFET, if it's shorted S-G hopefully the RT6585 detected the fault, that's why the 3.3V and 5V supplies don't work

You can remove PQ6204 and measure it outside the board to confirm, set the hot air to 450-460 C

With the MOSFET removed measure again S-G pads on the board, resistance should be higher
If the MOSFET is shorted S-G outside the board, it's definitely faulty

Always measure resistance without power applied, don't connect the battery/charger until the MOSFET is replaced with an appropriate one
Charger won't work anyway as the TPS65994 is missing from the board

Dammit, I measured S TO G AGAIN ON 6204 and got 1.7 meg. (I tripled checked this time). My bad. Thanks for the hot air setting too btw.

[m1ch43lzm]

I can't think of anything else that could cause the 3.3V and 5V supplies to not start, but the LDO outputs work
Maybe an out of spec resistor in that area, compare with the schematics, page 60 and the boardview

With power removed (no battery, no charger) measure resistance across PR6204 and PR6205, should be 2.2 ohms (meter may read a little higher due to probes resistance, note the value of the probes touching together)
PR6201: 15K
PR6202: 5.1k

With only battery connected, only if the MOSFETs and RT6585C IC are in place
If both enable signals 3VALW_EN and 5VALW_EN are present (3.3v) and the outputs at the inductors are not shorted to GND, it should work, supplying the 3.3V and 5V at the inductors PL6201 and PL6202

[bogart219]

I can't think of anything else that could cause the 3.3V and 5V supplies to not start, but the LDO outputs work
Maybe an out of spec resistor in that area, compare with the schematics, page 60 and the boardview

With power removed (no battery, no charger) measure resistance across PR6204 and PR6205, should be 2.2 ohms (meter may read a little higher due to probes resistance, note the value of the probes touching together)
PR6201: 15K
PR6202: 5.1k

With only battery connected, only if the MOSFETs and RT6585C IC are in place
If both enable signals 3VALW_EN and 5VALW_EN are present (3.3v) and the outputs at the inductors are not shorted to GND, it should work, supplying the 3.3V and 5V at the inductors PL6201 and PL6202

Those four resistors all checked out good. The only thing off the board now is the TPS chip and a cap PC5302. With the battery plugged in testing to ground those two solder pads you highlighted in the picture, the meter just kept flashing from 1.5 to 2.5 volts, back and forth.

[m1ch43lzm]

Those four resistors all checked out good. The only thing off the board now is the TPS chip and a cap PC5302. With the battery plugged in testing to ground those two solder pads you highlighted in the picture, the meter just kept flashing from 1.5 to 2.5 volts, back and forth.

That could be the cause of everything right now, those should be stable 3.3v

Measure resistance of RE4535 (it's smaller than a flea, near one BIOS chip UB2, your board has 2) and RE4539 (near the EC UE1, its a chip branded "Lenovo" IT8227VG), those are pullups for the 3.3V and 5V enable signals, both should measure 100K, why did the Lenovo engineers place them in completely different locations...

If the resistors are OK, maybe the issue is the EC, if it has black glue on the corners don't attempt to remove it, that glue that Lenovo likes is very difficult to remove, you may damage the pads on the board; also it's a BGA chip that would need to be reballed
Also the EC as far as I know needs to be programmed after replacement, and the programmer for those is very expensive

[bogart219]

That could be the cause of everything right now, those should be stable 3.3v

Measure resistance of RE4535 (it's smaller than a flea, near one BIOS chip UB2, your board has 2) and RE4539 (near the EC UE1, its a chip branded "Lenovo" IT8227VG), those are pullups for the 3.3V and 5V enable signals, both should measure 100K, why did the Lenovo engineers place them in completely different locations...

If the resistors are OK, maybe the issue is the EC, if it has black glue on the corners don't attempt to remove it, that glue that Lenovo likes is very difficult to remove, you may damage the pads on the board; also it's a BGA chip that would need to be reballed
Also the EC as far as I know needs to be programmed after replacement, and the programmer for those is very expensive

Both of those resistors checked out good. Yeah, I can't mess with that EC chip. It seems this flashing started after something I did but what? The question is is this flashing the result of a component touching a ground where it shouldn't (that would be a short right)? Or is a component getting power from two sources at once? I will examine the areas I screwed with again to see if I can find anything fishy. Thanks again my man, I'm finding out how difficult it can be to diagnose a motherboard problem when its sitting in front of you, let alone trying to find a problem posting back and forth with a noob such as myself!!!!!!!

[bogart219]

Mich, I'm just spit balling here and tell me what you think of this: I asked this above, The question is is this flashing the result of a component touching a ground where it shouldn't (that would be a short right)? Or is a component getting power from two sources at once? Now if the flashing is from a short to ground, you would think something would heat up wouldn't you? I just checked the board with the charger and battery plugged in with my thermal camera and the only thing I seen light up a little was the BQ chip and that was only at 80c. Now would it be feasible to try some voltage injection? I got a voltage injection tool a few days ago. at this point do you think that would tell us anything?